The first drink I buy when I land in Seoul is Achim Haetsal - I think its a sort of rice drink. Tastes gorgeous. Luckily they sell it in Korean stores in Tokyo too.
Shin Ookubo [新大久保] has a large Korean population so if you are looking for good Korean food and groceries then thats the place to go - get off at Shin Ookubo station on the JR Yamanote line.
